ADs/Doubles Swell Statistics, Spring: All Swell – Any Wind
The figure describes the combination of swells directed at ADs/Doubles through a typical northern hemisphere spring and is based upon 6580 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast wind or surf right at the coastline so we have chosen the best grid node based on what we know about ADs/Doubles. In this particular case the best grid node is 28 km away (17 miles).
The rose diagram illustrates the distribution of swell directions and swell sizes, while the graph at the bottom shows the same thing but without direction information. Five colours show increasing wave sizes. The smallest swells, less than 0.5m (1.5 feet), high are coloured blue. These occurred only 58% of the time. Green and yellow show increasing swell sizes and highest swells greater than >3m (>10ft) are shown in red. In each graph, the area of any colour is proportional to how commonly that size swell was forecast.
The diagram implies that the prevailing swell direction, shown by the largest spokes, was ENE, whereas the the dominant wind blows from the E. Because the wave model grid is away from the coast, sometimes a strong offshore wind blows largest waves away from ADs/Doubles and out to sea. We group these with the no surf category of the bar chart. To simplify things we don't show these in the rose plot. Because wind determines whether or not waves are good for surfing at ADs/Doubles, you can select a similar diagram that shows only the swells that were expected to coincide with glassy or offshore wind conditions. Over an average northern hemisphere spring, swells large enough to cause clean enough to surf waves at ADs/Doubles run for about 42% of the time.
IMPORTANT: Beta version feature! Swell heights are open water values from NWW3. There is no attempt to model near-shore effects. Coastal wave heights will generally be less, especially if the break does not have unobstructed exposure to the open ocean.